There are known chemically stable and inert oil compounds containing fluorine, for instance, polychlorotrifluoroethylene, perfluoropolyethers and perfluoroalkanes, for the applications indicated above. However, compounds containing chlorine can dechlorinate and corrode metal materials in the presence of water. See, for example, "Advanced Technology of Halogen Chemicals", pages 214 to 215, C.M.C. Co. (1984). Fluoridated oils, in particular perfluoropolyethers not containing hydrogen and/or chlorine atoms, have excellent stability for use in many applications.
In general however the perfluoropolyethers do not have sufficiently good anticorrosion properties for many applications.
Perfluoropolyether oils do not have sufficient surface activity for many purposes; see for example Shinku, vol. 28, No. 6, pp. 483-485 (1985) and Chemistry and Industry of the Magnetic Body, pages 52 to 55, Techmart Co., (1978). Even by adding organic acids as surface active agents to perfluoropolyethers, for instance, penta-(perfluoropropylene oxide)-perfluoropropanoic acid, desorption of the surface treating agent takes place at 65.degree. C., so that it is extremely difficult to improve the surface activity at temperatures higher than 65.degree. C. (Chemistry and Industry of the Magnetic Body, p. 39, cited above).
In addition to this, said perfluoropolyethers, though having excellent chemical stability, when containing the additives mentioned above have the disadvantage to corroding the metal surface. This must be completely avoided when the perfluoropolyethers are employed for magnetic media in which the magnetic substance itself is very fine metal powder.